Tracked load carrying vehicle

ABSTRACT

A tracked load carrying vehicle comprises a chassis (10); an engine (11) mounted on the chassis for propelling the vehicle; an output shaft (13) driven by the engine; two tracks (14,15) provided in parallel on either side of the chassis and each one running over a plurality of wheels (16-19,20-23), at least one of which being adapted to be driven by the output shaft (13) of the engine for driving the track; and a control lever (60) for steering the vehicle. A clutch is connected between the output shaft (13) of the engine and each one of the tracks (14,15), so that either one of the tracks can be disengaged. The control lever (60) is adapted to actuate one or the other of the clutches by means of a linkage, so that the clutch interrupts the transmission to the pertaining track (14,15). These features will give the vehicle a small turning radius and good maneuverability. The vehicle can also be provided with braking means for braking the tracks.

BACKGROUND OF THE INVENTION

The present invention relates to a tracked load carrying vehiclecomprising a chassis; an engine mounted on the chassis for propellingthe vehicle; an output shaft driven by the engine; two parallel tracksprovided on either side of the chassis, with each track running over aplurality of wheels, and with at least one wheel associated with eachtrack being adapted to be driven by the output shaft of the engine fordriving the track; and a control lever for steering the vehicle. Theload carrying vehicle is primarily intended as an aid for transportingheavy objects in woods and fields, all the year round. For example, suchvehicles may be used for pulling logs in the woods, for thetransportation of plants in connection with new plantation in clearings,and for the transportation of carcases in connection with hunting.

Load carrying vehicles for the above mentioned purposes are previouslyknown. These vehicles are either of the snow-scooter-type having tracksat the rear and turnable runners or wheels in front, or tracked specialvehicles having particular equipment, for example a hoist. These priorart vehicles have the disadvantage in common that they are difficult tohandle in wood-land where the free space available is limited, becauseof their limited steering capacity. Moreover, vehicles steered by meansof runners or wheels have a large turning radius, and prior art vehiclesof other types have had a low steering capacity or no steering capacityat all, so that a change of direction must be provided by turning thevehicle, for example, by forcefull pulling on an operating arm attachedto the vehicle. This later type operation is tiresome andtime-consuming.

It is known to steer tracked vehicles, particularly heavy trackedvehicles and armoured cars, by disengaging and/or braking one of thetracks while continuously driving the other track, thus providing aturning of the vehicle. This steering method requires complicatedmechanical steering devices which normally are controlled by a personwho rides in or on the vehicle. An example on this type of steering isdiclosed in U.S. Pat. No. 2,614,642.

It is also known to steer small load carrying vehicles by means of acontrol lever adapted to actuate a braking device for braking one or theother of two tracks or driving wheels. Such a device is disclosed in theU.S. Pat. No. 3,444,945. The steering device disclosed in this patent,however, comprises a differential, so that braking of one track entailsa faster driving of the other track. If one track skids, no drivingforce at all is obtained from the other track. Such a device is notsuitable for load carrying vehicles which must be operable under hardconditions in woods and fields all the year round.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide a tracked loadcarrying vehicle which is easy to steer, and therefore very easy tohandle even in difficult terrain, and which has a low weight and smallsize, so that it easily can be moved between different places.

The above object is achieved according to the present invention by atracked load carrying vehicle comprising: a chassis; an engine mountedon the chassis for propelling the vehicle; an output shaft driven by theengine; two parallel tracks provided one on either side of the chassis,with each track running over a plurality of wheels, and with each trackbeing adapted to be driven by the output shaft of the engine; arespective clutch disposed between the engine output shaft and eachtrack, with the clutches being arranged so that either one of the trackscan be disengaged from the output shaft of the engine; a control leverfor steering the vehicle, with the control lever being adapted to beturned around a substantially vertical shaft and being adapted toactuate one or the other of the clutches when turned from a neutralposition to one side or the other side, so that the clutch interruptsthe driving of the pertaining track; a cross arm provided for thecontrol lever, with each end of the cross arm being connected to arespective linkage arrangement adapted to transmit the turning motion tothe respective clutch; and each linkage arrangement consists of a linkarm, one end of which is pivoted on the cross arm and the other end ofwhich is provided with a projecting pin engaged within an aperture inone end of a pivotally mounted angle arm whose other end is adapted toengage with a movable portion of the clutch, the linkage arrangementbeing such that when the control lever is turned from a neutral positionto either side, the respective clutch on the side to which the lever ismoved is disengaged without affecting the clutch on the opposite side.

Due to the fact that the load carrying vehicle is provided with a clutchfor each track and a turnable control lever by means of which theclutches can be actuated, either one of the tracks easily and rapidlycan be disengaged from the engine. Therefore, the load carrying vehiclecan be turned with a very small turning radius in any direction and witha rapid change between different turning directions. The use of a crossarm attached to the control lever and a simple linkage for controllingthe clutches, which preferably are claw clutches, will make theconstruction simple and reliable. The provision of separate track brakesfor steering according to a further feature of the invention willfurther improve the maneuverability of the vehicle.

Due to the fact that one of the tracks can be disengaged from theengine, a heavy load, for example, when pulling logs of wood, can bestarted by running first one track, which is then supplied with the fullpower from the engine, and then engaging the other track, thus creatinga powerful jerk. Also comparatively heavy loads can be started with acomparatively low power engine, so that the weight as well as themanufacturing cost of the vehicle can be kept low.

The load carrying vehicle is intended to be steered by means of acontrol lever which is handled by a person walking in front of or besidethe vehicle, and the mentioned combination of the control lever and theclutches will then provide the special advantage that an automaticcorrection will be obtained in case the vehicle is skidding or ispulling diagonally, for example due to icy spots or mud. In case thevehicle unintentionally is turning diagonally to the desired direction,the track causing the diagonal movement due to a more powerfulpropulsion of the vehicle will be disengaged, so that the full enginepower can be used by the other track to return the vehicle to thedesired direction. As soon as the vehicle has recovered the desireddirection, the first track will again be engaged, so that both tracksagain propel with the same force. Due to this automatic correction ofdirection, the use of the vehicle on bad and rough roads is highlyfacilitated, particularly in the winter and in heavy rainfall andsnowfall. At the same time, the risk of diagonal pushing due to a heavyload pushing from behind on downhill slopes is considerably reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The vehicle according to the invention will now be described more indetail with reference to the attached drawings.

FIG. 1 is a perspective view of a tracked load carrying vehicleaccording to the invention.

FIG. 2 is an enlarged diagramatic plan view of the steering mechanismand the clutches for the vehicle shown in FIG. 1.

FIG. 3 is a view corresponding to that of FIG. 2, showing the steeringmechanism and the clutches in a position for turning the vehicle.

FIG. 4 shows a modified embodiment of the steering mechanism and theclutches according to FIGS. 2 and 3 including steering brakes for thetracks.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The tracked load carrying vehicle shown in FIG. 1 comprises a chassis 10and an engine 11, mounted on the chassis, for propelling the vehicle.The output shaft of the engine 12 is connected to a gear box 12 having atransverse output shaft 13 (FIG. 2) for transmission of the propellingpower from the engine 11.

The chassis 10 is further provided with two tracks 14,15 which arepositioned in parallel with each other on either side of the chassis.Each track runs over a plurality of guide wheel pairs 16-19 and 20-23,respectively, with the shafts of these wheel pairs being mounted inbearings in the chassis 10. The wheel pairs 17,18 and 21,22 are mountedin bearings at opposite ends of respective tiltable arms 24 and 25,which are pivotally mounted in bearings in respective bracket 26 and 27projecting from the chassis. The tiltable arms 24,25 are spring loadedby means of springs (not shown), so that the tracks 14 and 15 always arestretched. The wheels of the front wheel pair 16 and 20 for each trackare adapted to be driven by the output shaft 13 from the gear box 12 fordriving the tracks 14,15. The wheels are provided with projecting teeth(not shown), and the tracks are provided with corresponding apertures orperforations (not shown) in a conventional manner.

In the front, the vehicle is provided with a control lever 60 whoseoperation will be described in detail below.

The chassis 10 is also provided with a rotatably mounted clamp 29 foruse in pulling timber logs or for the attachment of a trailer, and witha vertically extending protection net 30 for protecting the engine 11.

The transmission from the output shaft 13 of the gear box 12 to thewheel pairs 16,20 is shown in FIG. 2. Each end of the output shaft 13 isprovided with a claw clutch 31 and 32, respectively. One portion 33 and34 of each clutch is rigidly connected to the output shaft 13 and theother portion 35 and 36 of each clutch is axially movably mounted on arespective rotatable intermediate shaft 37, 38. The intermediate shafts37 and 38 are connected to the track driving pair of wheels 16 and 20,respectively. The axially movable portion 35 and 36 of each claw clutchis spring loaded by means of a respective spring 39 and 40, so that itmeshes with the associated respective fixed portion 33, 34 on the outputshaft 13 and can be brought out of mesh by means of a respective angulararm 41, 42. Each angular arm is pivotally mounted on a respectivebracket 43, 44 projecting from the gear box 12. One end of each angulararm 41, 42 is forked and provided with a respective pair of pins 45, 46with only one pin of each pair being shown in FIGS. 2 and 3, as theother pin is on the opposite side of the respective shafts 37 and 38.The respective pairs of pins 45,46 engage with grooves 47 and 48,respectively, in the respective movable portions 35,36 of the clawclutches. The other end of each angular arm 41,42 is provided with anaperture 49, 50, respectively for engagement with a respective pin 51,52 provided at the rear end of an arm 53 and 54, respectively. Theforward ends of the arms 53,54 are pivotally mounted, by means ofrespective bearings on the respective ends of a cross arm 55. The crossarm 55 is pivotally mounted, at its center point, on a vertical shaft 56mounted on a bracket 57 which is rigidly attached to the gear box 12.The cross arm 55 is at its centre provided with a central forwardlyprojecting portion 58 carrying a horizontal pivot 59 on which thecontrol lever 60 is mounted. The pivot 59 is intented for positioningthe control lever 60, so that the lever 60 can be swivelled in a planeperpendicular to the plane of the cross arm 55.

In the modified embodiment shown in FIG. 4, the chassis 10 of thevehicle is provided with two brackets 61,63 on either side of the gearbox 12. Each one of these brackets 61,63 carries a respectivereplaceable brake cone 62, 64, mounted such that it cannot rotate in thesame direction as the associated intermediate shaft 37, 38. Each of themoveable clutch portions 35, 36 has a conical shape at its outer end,i.e., the end facing away from the gear box 12, with these conical endsbeing adapted to engage with the fixed brake cones 62 64, respectivelyso that the cones can operate as steering brakes, as shown in the leftportion of FIG. 4.

The operation of the steering means will now be described with referenceto FIGS. 2 and 3. When the control lever 60 is in the straight forwardor neutral position shown in FIG. 2, i.e., parallel to the longitudinalcentral axis of the vehicle, both claw clutches 31,32 are in engagement,so that the power from the engine 11 is transmitted equally to bothparallel tracks. The vehicle is then propelled straight ahead. When thevehicle has to be turned, the control lever 60 is moved in the directionof the desired turn, for example to the left, as shown in FIG. 3. Thiswill cause the cross arm 55 to be turned, so that the arms 53 and 54 aremoved. The arm 53 will then be pushed towards the angular arm 41, sothat this arm is turned (clockwise in FIG. 3), thus moving the movableportion 35 of the claw clutch 31 toward the left in FIG. 3 against theforce of the spring 39, so that the clutch portions 33 and 35 aredisengaged. The transmission of power from the output shaft 13 to theintermediate shaft 37 and the wheel pair 16 for the track 14 is thusinterrupted, so that the track 14 stops or only moves due to themovement of the vehicle. The other claw clutch 32 is not actuated by thechanged direction of the control lever, as the pin 52 of the arm 54 ismerely lifted a small distance in the aperture 50 of the angular arm 42.Thus, the propelling of the other track 15 is continued and this trackcan then use the full power from the engine. The vehicle will then turnaround its vertical central axis with a very small turning radius.

The vehicle can be turned to the right by moving the control lever tothe right in a corresponding way.

In the case when the vehicle is provided with separate steering brakes35,64,63 and 36,62,61, respectively, according to FIG. 4, thetransmission of power to the track will be interrupted and the trackwill also be braked, when the control lever 60 is turned to its endposition, i.e. when the movable portion 35 or 36 of the claw clutch isin engagement with the brake cone 64 or 62, respectively. The brakecones are, by means of the brackets 63 and 61, rigidly attached to thechassis 10 of the vehicle.

The control lever 60 is pivoting around the shaft 56, which issubstantially vertical in normal use of the vehicle, so that a change ofturning direction can be made rapidly, as well as around thesubstantially horizontal pivot 59, so that the control lever 60 can bekept at a comfortable level for work. The control lever 60 may beprovided with a control for adjusting the rotation speed of the engine.

Due to the design of the steering means with two clutches forinterrupting the transmission to one or the other of the tracks, acomparatively low power engine can be used, for example a gasolineengine of about 5 Hp. The engine 11 is preferably provided with acentrifugal clutch, so that the shaft of the engine is connected to thegear box 12 when the rotational speed of the engine exceeds a certainlimit. This may be achieved by appropriately controlling the supply ofgasoline to the engine by means of the throttle control 61 attached tothe control lever 60. This will avoid a separate clutch control.

While only two embodiments of the tracked load carrying vehicleaccording to the invention have been described and shown, it is evidentthat many modifications and variations are possible within the scope ofthe invention. For example, instead of claw clutches, friction clutchescan be used, and instead of the illustrated wheel pairs, driving rollscan be used. As an alternative, the wheels can be provided in a bogie,and the bogie can then be attached to the chassis or form the chassis.The control lever can also be arranged so that the vehicle can besteered from beside the vehicle, which may be an advantage, for example,when heavy loads have to be transported down steep hills. The steeringbrakes can alternatively be designed for direct, firm locking, forexample by means of teeth or jaws.

I claim:
 1. A tracked load carrying vehicle comprising: a chassis; anengine mounted on said chassis for propelling the vehicle; an outputshaft driven by said engine; two parallel tracks provided one on eitherside of said chassis, with each said track running over a respectiveplurality of wheels; means for driving said tracks including respectiveclutches connected between said output shaft of said engine and at leastone of said wheels associated with each of said tracks with saidclutches being arranged so that either one of said tracks can bedisengaged from said output shaft; a control lever for steering thevehicle; a cross arm connected to said control lever; means for mountingsaid control lever and said cross arm on said chassis such that they canbe turned together about a substantially vertical shaft; and first andsecond linkage means, each connected between said cross arm and arespective one of said clutches and each responsive to the turning ofsaid control lever from a neutral position toward a respective side ofthe vehicle, for activating the one of said clutches on the side towhich said lever is turned to interrupt the driving of the associatedsaid track by said drive shaft without affecting the clutch of the otherside of the vehicle, each of said linkage means including a link armhaving one of its ends pivotally mounted on a respective end of saidcrossbar and its other end provided with a projecting pin, and apivotally mounted angular arm having an aperture at one end which isengaged by said projecting pin of said link arm and means at the otherend of said angle arm for engaging the moveable portion of theassociated one of said clutches.
 2. A vehicle according to claim 1wherein said angular arms are pivotally mounted on brackets which arerigidly attached to said chassis.
 3. A vehicle according to claim 1wherein said cross arm of said control lever is pivotally mounted onsaid substantially vertical shaft which forms the vertical pivot forsaid control lever and which is rigidly secured to said chassis, andsaid control lever pivotally mounted on a horizontal shaft disposed onsaid cross arm.
 4. A vehicle according to claim 1 wherein said clutchesare claw clutches, with one portion of each said claw clutch beingrigidly attached to said output shaft of said engine and with the otherportion of each said clutch being movable on a respective intermediateshaft provided to transmit the power from said output shaft of theengine to the respective said track.
 5. A vehicle according to claim 4wherein said movable portion of each of said clutches is adapted tocooperate with a respective brake means rigidly attached to said chassisfor braking the respective said track.
 6. A vehicle according to claim 5wherein said movable portion of each said clutch is provided with aconical end, and each said brake means includes a respective brake coneattached to said chassis of the vehicle and adapted to cooperate withsaid conical end of the respective said movable portion for braking therespective said track when said control lever is positioned in one orthe other of its end positions.
 7. A vehicle according to claim 1wherein said chassis is provided with a rotatably mounted clamp providedfor the transportation of timber logs or for attaching a trailer to saidchassis.
 8. A vehicle according to claim 1 wherein said movable portionof each of said clutches is adapted to cooperate with a respective brakemeans rigidly attached to said chassis for braking the respective saidtrack.
 9. A vehicle according to claim 8 wherein said movable portion ofeach said clutch is provided with a conical end, and each said brakemeans includes a respective brake cone attached to said chassis of thevehicle and adapted to cooperate with said conical end of the respectivesaid movable portion for braking the respective said track when saidcontrol lever is positioned in one or the other of its end positions.